A vehicle battery is an electrochemical device that includes one or more cells that convert chemical energy to electric energy. Currently, automobile batteries are “12-volt” direct-current (DC) batteries that supply approximately 12.6 volts. Conventional 12-volt batteries typically include six series-connected cells, which produce approximately 2.1 volts.
When a driver starts an engine of a vehicle, the starter draws current from the battery and reduces the charge on the battery. A charging system recharges the battery and typically includes an alternator (or generator), a voltage regulator, and an optional charge indicator. The generator is a direct current (DC) generator that converts mechanical movement of the engine into electrical power that charges the battery. The voltage regulator regulates output voltage and current levels produced by the generator. The charge indicator provides a visual indication of the operational health of the charging system and/or the battery.
Once the engine is running, the charging system charges the battery and powers other electrical systems and loads associated with the vehicle. Some of the electrical loads of the vehicle may include, for example, heating ventilation and air-conditioning (HVAC) blowers, an air-conditioning (AC) compressor clutch, heated seats, heated mirrors, a window defogger, window wipers, courtesy door lights, interior lights, engine cooling fans, etc.
The voltage regulator maintains the output voltage of the generator within a voltage range, such as 13 to 16 volts. When the voltage stays within the voltage range, the generator can perform several functions. The generator can charge the battery, and can supply power to the other vehicle electrical systems and loads. Problems associated with undercharging or overcharging of the battery are also prevented. If the battery is undercharged, the battery cannot crank and start the engine. If the battery is overcharged, the battery may overheat and/or experience “gassing” (the formation of acid fumes within the battery) and become permanently damaged.
The voltage regulator adjusts the output voltage of the generator based on the temperature of the battery and the state of charge (SOC) of the battery. However, conventional temperature and SOC monitors are expensive and not accurate. Conventional temperature and SOC monitors also require a significant amount of extra wiring and additional electronic components.